Good morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 12, at 7:30 a.m. Montana Fish, Wildlife & Park Snowmobile Program, in cooperation with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
Overnight a trace to one inch of snow fell over much of our forecast area. Currently, winds are blowing out of the WSW at 5-15 mph and mountain temperatures are in the high single digits to low teens F. Today, mountain temperatures will warm into the high 20’s to low 30’s F and winds will stay light out of the WSW at 5-15 mph. Skies will be partly cloudy this morning, but will gradually become mostly cloudy by this afternoon. A slight chance of mountain snow showers will arrive later tonight. 1-2 inches is possible in the mountains by tomorrow morning.
The Bridger Range, the Madison and Gallatin Ranges, and the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
West to southwest winds blowing up to 80 mph stripped exposed windward slopes Thursday night into Friday. The Big Sky ski patrol reported that strong winds eroded 1-2 feet of snow off upper elevation slopes during the past couple of days - uncovering old crown lines that have not been seen since January. As snow disappears off some slopes, it is being deposited on others. Luckily, newly formed wind drifts have bonded well to the old snow surface helping reduce the chances of triggering a slide. Calmer winds and warmer temperatures over the past 24 hours have also helped stabilize wind loaded slopes.
However, triggering a pocket of wind deposited snow is not impossible. Yesterday, the Moonlight Basin Ski Patrol triggered a medium sized wind slab with explosives. They also observed two small avalanches on wind loaded slopes on Thursday (photo). Avalanches will likely stay confined to specific wind loaded areas and initiating long propagating cracks will be unlikely. The best approach today throughout our area is identifying and avoiding steep wind loaded slopes. Also, strong winds have added yet another layer to already large overhanging cornices. Avoiding slopes directly under cornices and giving them a wide berth along ridgelines will be a good way to avoid being run over by a car or house sized chunk of snow.
A secondary concern will be the possibility of wet loose avalanches on steep, south facing slopes. If the sun shines for an extended period of time, obvious clues such as roller balls and point releases will be bull’s eye data the surface snow is losing cohesion and strength. Keeping your thinking cap on and paying attention to changing conditions will be the best way to avoid being surprised.
Today, human triggered avalanches are possible on wind loaded slopes, which have a MODERATE avalanche danger. Slopes that have not received a wind load have a LOW avalanche danger.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations, drop us a line at mtavalanche@gmail.com or call us at 587-6984.
“How To” Video Tutorials
We created three videos on the Stability Tests page describing how to perform a Compression Test, an Extended Column Test, and how to choose a snowpit location.